Plating apparatus and plating method

ABSTRACT

There is provided a plating apparatus and method which can control the temperature of a plating solution during plating more uniformly and easily form a uniform plated film on the to-be-plated surface of a workpiece, and which can simplify the device and decrease the footprint. The plating apparatus includes a plating bath having a double bath structure including an inner bath for holding a plating solution and carrying out plating, and an outer bath which surrounds the inner bath and is in fluid communication therewith. A heating device is disposed in the outer bath. The plating apparatus may further include means for circulating or stirring the plating solution in the plating bath.

TECHNICAL FIELD

This invention relates to a plating apparatus and plating method. Moreparticularly, the invention relates to an electroless plating apparatusand method useful for forming embedded interconnects, in which anelectric conductor, such as copper or silver, is imbedded in finerecesses for forming interconnects in the surface of a substrate like asemiconductor substrate, and for forming a protective layer forprotecting the surface of the interconnects.

BACKGROUND ART

An electroless plating is such a method that a plated film is formed ona plating surface of a workpiece by chemically reducing metal ions in aplating solution without supplying any electric current from theoutside, and the electroless plating is widely used in anickel-phosphorus plating and a nickel-boron plating for giving acorrosion resistance and a wear resistance, and a copper plating for aprinted-wiring substrate.

As an electroless plating apparatus, there has been generally known anapparatus comprising a plating bath for holding an electroless platingsolution which overflows during plating process, and a verticallymovable holding portion disposed above the plating bath for holding aplating workpiece, such as a substrate, whereby the workpiece held bythe holding portion is dipped into the plating solution in the platingbath. This kind of plating apparatus is provided with a plating solutionregulating device separately for regulating the temperature, thecomponents, etc. of the plating solution. The temperature and thecomponents of the plating solution that has been overflowed from theplating bath is regulated in the plating regulating device, and thenplating solution is supplied to the plating bath.

In recent years, as the processing speed and integration of asemiconductor chip becomes higher, there has been a growing tendency toreplace aluminum or aluminum alloy with copper having a low electricresistivity and a high electromigration resistance as metallic materialsfor forming interconnection circuits on the semiconductor substrate.These kind of copper interconnects are generally formed by filling finerecesses formed in the surface of the substrate with copper. As a methodfor forming the copper interconnects, CVD, sputtering, and plating areknown, but plating is generally used. In any case, after a copper filmis deposited on the surface of the substrate, the surface of thesubstrate is polished to a flat finish to remove the plated copper onthe surface of the substrate by a chemical mechanical polishing (CMP)process.

In the case of interconnects formed by such a process, the embeddedinterconnects have an exposed surface after the flattening processing.When an additional embedded interconnect structure is formed on such anexposed surface of interconnects of a semiconductor substrate, thefollowing problems may be encountered. For example, during the formationof a new SiO₂ interlevel dielectric, the exposed surface of thepre-formed interconnects is likely to be oxidized. Further, upon etchingof the SiO₂ layer for the formation of contact holes, the pre-formedinterconnects exposed at the bottoms of the contact holes can becontaminated with an etchant, a peeled resist, etc. Moreover, in thecase of copper interconnects, there is a fear of copper diffusion.

In view of this, in the case of copper interconnects, for example, itmay be considered to selectively cover the surface of copperinterconnects with a protective layer (plated film) of a Ni—B alloy orthe like, having a good adhesion to copper and a low resistivity (ρ).The Ni—B alloy layer can be formed on the surface of e.g. copperselectively by using an electroless plating solution that containsnickel ions, a complexing agent for nickel ions and an alkylamine boraneor a borohydride compound as a reducing agent for nickel ions and byimmersing the surface of the substrate in the electroless platingsolution.

An electroless plating is applied to main filling materials (Cu) for thecopper interconnects, the formation of the seed layer on the barriermetal, or the reinforcement of the seed (Cu), to further the formationof the barrier metal itself, or the formation of cap material for thecopper interconnect (in any case, Ni—P, Ni—B, Co—P, Ni—W—P, Ni—Co—P,Co—W—P, Co—W—B), or the like. In any electroless plating process,uniformity of the film thickness over an entire surface of the substrateis required.

In electroless plating, when a plating surface of a workpiece is broughtinto contact with an electroless plating solution, a plating metalinstantly begins to deposit on the plating surface of the material, andthe deposition rate of the plating metal varies depending on thetemperature of the plating solution. Accordingly, in order to form aplated film having a uniform film thickness on the plating surface of aworkpiece, the temperature of a plating solution is required to beuniform all over the surface of the material from the initial time ofcontact between the workpiece and the plating solution, and the uniformplating temperature must be kept throughout the plating treatment.

In conventional electroless plating apparatuses, a plating solutionheated to a predetermined temperature is supplied to a plating bath orto the plating surface of a workpiece. However, the temperature of theplating solution is likely to change (lower) during transportation ofthe plating solution or in the course of plating. Even when the platingsolution in the plating bath is heated by a heater or the like built ina substrate holder, it has been difficult to control the platingsolution at a constant temperature throughout the plating treatment.Further, in order to secure the uniformity of plating over the entireplated surface, uniformity of the flow of plating solution in a platingbath is required in addition to the uniformity of plating temperature.In this connection, if a plating solution in a plating bath is alwayscirculated or stirred, it is difficult to create a uniform flow ofplating solution over the surface of a workpiece. Conversely, if aplating solution in a plating bath is not circulated or stirred, it isdifficult to keep the temperature of the plating solution uniformthroughout the solution.

The rate of electroless plating and the quality of plated film dependlargely on the temperature of the electroless plating solution. In orderto secure uniformity of the film thickness over the entire surface of aworkpiece to be processed, it is desired to control the variation of theplating solution temperature within the range of ±1° C. over the entiresurface of the workpiece to be processed. However, according toconventional electroless plating apparatuses, a temperature variation inthe order of ±5° C. is generally produced during plating in the platingsolution held in a plating bath, since the temperature of the platingsolution is likely to change in the course of the plating process, andhence it is difficult to meet the ±1° C. variation requirement. Further,the plating apparatus occupies a considerably large space and iscomplicated, since the plating apparatus includes the plating bath andthe plating solution regulating device. Electroplating apparatuses arethe same as the above-described situation.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above situation inthe related art. It is therefore an object of the present invention toprovide a plating apparatus and method which can control the temperatureof a plating solution during plating more uniformly and easily form auniform plated film on the to-be-plated surface of a workpiece, andwhich can simplify the apparatus and decrease the footprint.

In order to achieve the above object, the present invention provides aplating apparatus, comprising: a plating bath of a double bath structureincluding an inner bath for holding a plating solution and carrying outplating, and an outer bath which surrounds the inner bath and is influid communication therewith; and a heating device disposed in theouter bath.

By providing the plating bath of a double bath structure consisting ofthe inner and outer baths and disposing the heating device in the outerbath, the apparatus can be simplified and the footprint can be madesmall. Further, since the plating solution in the inner bath can beheat-insulated and kept warm by the plating solution in the outer bath,the plating solution can be controlled at a uniform temperature duringplating, and a uniform plated film can be formed with ease on theto-be-plated surface of a workpiece.

The inner bath and the outer bath may be partitioned from each other byan inner wall having a number of communication holes formed in theentire inner wall. The outer bath may be a closed-type bath.

The heating device may comprise a heating tube for passing a heatingmedium therethrough.

In a preferred embodiment, the plating apparatus further comprises means(i.e., a blending system) for circulating or stirring the platingsolution in the plating bath. By circulating or stirring the platingsolution in the plating bath, the temperature of the plating solution,which is kept heated by the heating device disposed in the outer bath,can be kept more uniform throughout the plating solution.

The blending system for circulating the plating solution in the platingbath may be a plating solution circulation system. The plating solutioncirculation system preferably is adapted to withdraw the platingsolution from the inner bath and return it to the outer bath. Analternative is to withdraw the plating solution from the outer bath andreturn it to the inner bath. (The circulation direction is opposite thatshown in FIG. 2.)

The blending system for stirring the plating solution in the platingbath may be a stirring device. The stirring device is preferably locatedalmost in the center of the inner bath.

The present invention also provides a plating method, comprising:plating a workpiece in a plating apparatus by allowing the platingsurface of the workpiece to be in contact with a plating solution, theplating apparatus including: a plating bath of a double bath structureincluding an inner bath for holding the plating solution and carryingout the plating, and an outer bath which surrounds the inner bath and isin fluid communication therewith; a heating device disposed in the outerbath; and means (a blending system) for circulating or stirring theplating solution in the plating bath, wherein the circulation orstirring of the plating solution in the plating bath is stopped duringplating.

By thus stopping the flow of plating solution in the plating bath duringthe progress of plating, the flow of plating solution can be preventedfrom influencing the good or poor results of plating. Further, apossible natural convection of the plating solution in the plating bathcan be counteracted by a flow of plating solution which will be createdwhen the workpiece is rotated.

The workpiece is preferably rotated at a low speed during plating.

The above and other objects, features, and advantages of the presentinvention will be apparent from the following description when taken inconjunction with the accompanying drawings which illustrates preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A through 1D are diagrams illustrating, in sequence of processsteps, an example of the formation of copper interconnects by copperplating and the formation of protective layer for the copperinterconnects;

FIG. 2 is a cross-sectional view of an electroless plating apparatusaccording to an embodiment of the present invention;

FIGS. 3A through 3C are diagrams illustrating the flow state of aplating solution in a plating bath upon plating;

FIG. 4 is a cross-sectional view of an electroless plating apparatusaccording to another embodiment of the present invention;

FIG. 5 is a plan view showing the layout of a plating treatmentapparatus which is provided with the electroless plating apparatus shownin FIGS. 2 and 3;

FIG. 6 is a plan view showing the layout of another plating treatmentapparatus which is provided with the electroless plating apparatus shownin FIGS. 2 and 3;

FIG. 7 is a plan view of an example of a substrate plating apparatus;

FIG. 8 is a schematic view showing airflow in the substrate platingapparatus shown in FIG. 7;

FIG. 9 is a cross-sectional view showing airflows among are as in thesubstrate plating apparatus shown in FIG. 7;

FIG. 10 is a perspective view of the substrate plating apparatus shownin FIG. 7, which is placed in a clean room;

FIG. 11 is a plan view of another example of a substrate platingapparatus;

FIG. 12 is a plan view of still another example of a substrate platingapparatus;

FIG. 13 is a plan view of still another example of a substrate platingapparatus;

FIG. 14 is a view showing a plan constitution example of thesemiconductor substrate processing apparatus;

FIG. 15 is a view showing another plan constitution example of thesemiconductor substrate processing apparatus;

FIG. 16 is a view showing still another plan constitution example of thesemiconductor substrate processing apparatus;

FIG. 17 is a view showing still another plan constitution example of thesemiconductor substrate processing apparatus;

FIG. 18 is a view showing still another plan constitution example of thesemiconductor substrate processing apparatus;

FIG. 19 is a view showing still another plan constitution example of thesemiconductor substrate processing apparatus;

FIG. 20 is a view showing a flow of the respective steps in thesemiconductor substrate processing apparatus illustrated in FIG. 19;

FIG. 21 is a view showing a schematic constitution example of a beveland backside cleaning unit;

FIG. 22 is a vertical sectional view of an example of an annealing unit;and

FIG. 23 is a transverse sectional view of the annealing unit.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings, which in no waylimit the invention.

FIGS. 1A through 1D illustrate, in sequence of process steps, an exampleof the formation of copper interconnects in a semiconductor device. Asshown in FIG. 1A, an insulating film 2 of, for example, SiO₂ isdeposited on a conductive layer 1 a in which semiconductor devices areprovided, which is formed on a semiconductor base 1. Contact holes 3 andtrenches 4 for interconnects are formed in the insulating film 2 by thelithography/etching technique. Thereafter, a barrier layer 5 of TaN orthe like is formed on the entire surface, and a copper seed layer 6 asan electric supply layer for electroplating is formed on the barrierlayer 5, for example, by sputtering.

Thereafter, as shown in FIG. 1B, copper plating is carried out onto thesurface of the semiconductor substrate W to fill the contact holes 3 andthe trenches 4 with copper and, at the same time, deposit a copper film7 on the insulating film 2. Thereafter, the copper film 7 and thebarrier layer 5 on the insulating film 2 are removed by chemicalmechanical polishing (CMP) so as to make the surface of the copper film7 filled in the contact holes 3 and the trenches 4 for interconnects andthe surface of the insulating film 2 lie substantially on the sameplane. Interconnects 8 composed of the copper seed layer 6 and thecopper film 7, as shown in FIG. 1C, are thus formed in the insulatinglayer 2. Next, electroless Ni—B plating, for example, is carried outonto the surface of the substrate W to form a protective layer (platedfilm) 9 composed of a Ni—B alloy selectively on the exposed surface ofcopper interconnects 8 to protect the interconnects 8, as shown in FIG.1D.

FIGS. 2 and 3 show an electroless plating apparatus according to anembodiment of the present invention. The electroless plating apparatus10 can be used, for example, for the formation of the barrier layer 5 ofFIG. 1, the reinforcement of the copper seed layer 6 and the depositionof the copper film 7, and also for the formation of the protective layer(plated film) 9.

The electroless plating apparatus 10 includes an upwardly-open innerbath 14 for holding a plating solution 12 and carrying out plating, anda substrate holder 16, disposed at the top opening of the inner bath 14,for holding a substrate (workpiece) W, such as a semiconductor wafer,with its front surface (to-be-plated surface) facing downward (facedown) or upward (face up).

The inner bath 14 constitutes the inner bath of a plating bath 18 havinga double bath structure. Specifically, the plating bath 18 includes theupwardly-open inner bath 14 defined by an inner wall 20, and a closedouter bath 26 defined between the inner wall 20 and an outer wall 24that surrounds the sides and bottom of the inner wall 20. A number ofcommunicating holes 20 a for allowing the inner bath 14 to communicatewith the outer bath 26 are formed in the entire inner wall 20, so thatthe plating solution 12 in the inner bath 14 is in direct communicationwith the plating solution 12 in the outer bath 26, and so that bothbodies of plating solution in the plating bath 18 always lie on the samelevel.

In the outer bath 26, there is provided a heating device which comprisesa heating tube 30, according to this embodiment, for passingtherethrough a heating medium and for heating the plating solution 12 inthe outer bath 26 to for example 70° C.

The plating apparatus is also provided with a plating solutioncirculation system 32 (a blending system) for circulating the platingsolution 12 in the plating bath 18, i.e. the plating solution 12 in theinner bath 14 and the outer bath 26. The plating solution circulationsystem 32 comprises a circulation pump 34, a plating solution dischargepipe 36 which connects the discharge outlet of the circulation pump 34with the outer bath 26, a filter 39 and a plating solution suction pipe38 which connects the suction inlet of the circulation pump 34 with theinner bath 14. The circulation pump 34, when actuated, sucks the platingsolution 12 from the inner bath 14 and returns it to the outer bath 26.The plating solution 12 in the inner bath 14 and the outer bath 26 isthus circulated, whereby the temperature of the plating solution 12 inthe plating bath 18 can be kept uniform.

Further, by heating the plating solution 12 in the course of itscirculation by a heating tube (heating device) 30 disposed in the outerbath 26, and especially by shutting off (separating) the platingsolution 12 in the inner bath 14 from the plating solution 12 in theouter bath 26, the retention of the temperature of the plating solution12 can be made with ease and the plating solution 12 in the plating bath18 can be controlled at a constant temperature. The temperature of theplating solution 12 is generally 25 to 90° C., preferably 55 to 85° C.,more preferably 60 to 80° C.

The substrate holder 16 is designed so that it can hold the substrate Wby for example attraction, and can rotate and vertically move with thesubstrate W held by it.

In operation of the electroless plating apparatus of this embodiment,the circulation pump 34 is driven to circulate the plating solution 12in the plating bath 18. At the same time, a heating medium is introducedinto the heating tube 30 to heat the plating solution 12 in the outerbath 26. The heated plating solution 12 is directly introduced into theinner bath 14. The plating solution 12 in the plating bath 18 is thuscontrolled at a constant temperature, e.g. 70° C. On the other hand, thesubstrate holder 16 is raised relative to the inner bath 14, and thesubstrate holder 16 holds on its lower surface the substrate W by forexample attraction.

While the plating solution 12 is kept heated by continued introductionof the heating medium into the heating tube 30, the actuation of thecirculation pump 34 is stopped to thereby stop the circulation of theplating solution 12 in the plating bath 18 (i.e., stop the functioningof the blending system). Under these conditions, the substrate holder 16is lowered so as to immerse the substrate W held by the holder 16 in theplating solution 12 in the inner bath 14 to carry out plating of thefront surface (to-be-plated surface) of the substrate W for severalminutes. During the plating, if necessary, the substrate W is rotated ata low speed (e.g. 1-20 rpm). In other words, the holder 16 can operateindependently of the circulation pump 34 (i.e., independently of theblending system) so as to rotate the substrate even if the blendingsystem is not operating. It has been confirmed that even when theelectroless plating is carried out for several minutes under suchconditions, the temperature of the plating solution 12 can be controlledwithin the variation range of ±1° C. during the plating by continuingthe heating of the plating solution 12.

FIGS. 3A to 3C illustrate the flow state of the plating solution 12 uponthe plating at this time. Though the plating solution 12 is notcirculated, the plating solution 12 in the inner bath 14 is heatedexternally by the heating tube 30. Accordingly, as shown in FIG. 3A,there may be created a natural convection of the plating solution, forexample a flow of plating solution which ascends on the outer orperipheral side of the inner bath 14 and descends on the inner orcentral side thereof. On the other hand, when the substrate W, locatedin the inner bath 14 on its upper side and immersed in the platingsolution, is rotated at a low speed, as shown in FIG. 3B, there iscreated a flow of plating solution which ascends on the inner or centralside of the inner bath 14 and descends on the outer or peripheral sidethereof. Therefore, as a result of the combination of the two flows, theplating solution 12 in the inner bath 14 can be brought into astationary state, especially in the vicinity of the surface(to-be-plated surface) of the substrate W, as shown in FIG. 3C.

Electroless plating, in general, is sensitively influenced by a flow ofplating solution, and the flow of plating solution can be made uniformwith difficulty. In this regard, according to this embodiment of thepresent invention, the flow of the plating solution 12 in the inner bath14 is stopped during the progress of plating, as described above. Thiscan prevent the flow of plating solution from influencing the good orpoor results of plating. In addition, the possible natural convection ofthe plating solution 12 in the inner bath 14 can be counteracted by theflow of plating solution due to rotation of the substrate W, resultingin a stationary bath of the plating solution 12 during the platingprocess. This makes it possible to form a uniform plated film withoutsuffering from a flow of plating solution.

After completion of the plating, the substrate holder 16 is raised, andthen transferred to a cleaning position etc. While rotating thesubstrate W, a cleaning liquid is jetted from a cleaning liquid nozzle(not shown) toward the plated surface of the substrate W, therebycooling and, at the same, diluting and cleaning the plated surface,whereby the electroless plating reaction is terminated.

Thereafter, the plated substrate held by the substrate holder 16 istaken, for example by a hand of a robot, and is sent to the next processstep.

FIG. 4 shows an electroless plating apparatus 10 a according to anotherembodiment of the present invention. The electroless plating apparatus10 a differs from the electroless plating apparatus 10 shown in FIGS. 2and 3 in that the blending system comprises a stirring blade 42 of astirring device 40 disposed in almost the center of the inner bath 14,and the plating solution 12 in the plating bath 18 is stirred by therotation of the stirring blade 42. The remaining construction is thesame as shown in FIGS. 2 and 3, and hence the description thereof isomitted, giving the same reference numeral to the same or correspondingmember.

FIG. 5 shows the general construction of a plating treatment apparatuswhich is provided with the electroless plating apparatus 10 and carriesout a series of plating treatments. The plating treatment apparatusincludes pairs of electroless plating apparatuses 10, loading/unloadingsections 70, pre-plating treatment apparatuses 72 for carrying out apre-plating treatment, such as a catalyst-imparting treatment to impart,for example, a Pd catalyst to a surface of a substrate or an oxidefilm-removing treatment to remove an oxide film adhering to the exposedsurface of interconnects, temporary storage sections 74 capable ofcarrying out a rough cleaning, and post-cleaning apparatuses 76. Theplating treatment apparatus is also provided with a first transferdevice 78 a for transferring a substrate W between the loading/unloadingsections 70, the post-cleaning apparatuses 76 and the temporary storagesections 74, and a second transfer device 78 b for transferring thesubstrate W between the electroless plating apparatuses 10, thepre-plating treatment apparatuses 72 and the temporary storage sections74.

A description will now be given of a series of plating treatment processsteps performed by the above-described plating treatment apparatus.First, a substrate W held in the loading/unloading section 70 is takenout by the first transfer device 78 a, and the substrate is placed inthe temporary storage section 74. The second transfer device 78 btransfers the substrate W to the pre-plating treatment apparatus 72,where the substrate is subjected to a pre-plating treatment, such as acatalyst-imparting treatment using, for example a PdCl₂ solution, or anoxide film-removing treatment for removing an oxide film adhering to theexposed surface of interconnects, and the treated substrate W is thenrinsed.

Thereafter, the second transfer device 78 b transfers the substrate W tothe electroless plating apparatus 10, where an electroless platingtreatment is carried out using a predetermined plating solution having apredetermined reducing agent. Next, the second transfer device 78 btakes the plated substrate out of the electroless plating apparatus 10and carries the substrate to the temporary storage section 74. Roughcleaning of the substrate is carried out in the temporary storagesection 74. Thereafter, the first transfer device 78 carries thesubstrate to the post-cleaning apparatus 76, where a finish cleaning,for example by a pencil sponge, and spin-drying of the substrate arecarried out. After the cleaning, the first transfer robot 78 a returnsthe substrate to the loading/unloading section 70. The substrate islater sent to a plating apparatus or to an oxide film-forming apparatus.

FIG. 6 shows the general construction of a plating treatment apparatuswhich performs a series of plating treatments (cap plating treatments)for forming the protective layer 9 shown in FIG. 1D. The platingtreatment apparatus includes a pair of loading/unloading sections 80, apretreatment section 82, a Pd-imparting treatment section 84, apre-plating treatment section 86, the electroless plating apparatus 10and a cleaning/drying treatment section 88. The plating treatmentapparatus is also provided with a transfer device 92 which can movealong a transfer route 90 and transfers a substrate between the sectionsand apparatus.

A series of plating treatment (cap plating treatment) process steps asperformed by this plating treatment apparatus will now be described.First, a substrate W held in the loading/unloading section 80 is takenout by the transfer device 92 and transferred to the pretreatmentsection 82, where a pretreatment of the substrate, for examplere-cleaning of the surface of the substrate, is carried out. The cleanedsubstrate is transferred to the Pd-imparting treatment section 84, wherePd is adhered to the surface of copper film 7 (see FIG. 1C) to activatethe exposed surface of copper film 7. Thereafter, the substrate istransferred to the pre-plating treatment section 86, where a pre-platingtreatment, such as a neutralization treatment, is carried out to thesubstrate. Next, the substrate is transferred to the electroless platingapparatus 10, where a selective electroless plating, for example of aCo—W—P alloy, is carried out onto the activated surface of copper film7, thereby forming a Co—W—P film (protective layer) 9 on the exposedsurface of copper film 7 to protect the exposed surface, as shown inFIG. 1D. A plating solution containing a cobalt salt and a tungsten saltand, as additives, a reducing agent, a complexing agent, a pH buffer anda pH adjusting agent, for example, may be used as an electroless platingsolution in the electroless plating.

Alternatively, an electroless Ni—B plating may be carried out on theexposed surface (after polishing) of the substrate to selectively form aprotective layer (plated film) 9 composed of an Ni—B alloy film on theexposed surface of interconnects 8 to protect the interconnects 8. Thethickness of the protective layer 9 is generally 0.1 to 500 nm,preferably 1 to 200 nm, more preferably 10 to 100 nm.

As an electroless Ni—B plating solution for forming the protection layer9 of the Ni—B alloy film, use may be made of a solution which containsnickel ions, a complexing agent for nickel ions and an alkylamine boraneor a borohydride compound as a reducing agent for nickel ions, and whichis adjusted to a pH of 5-12 by using TMAH (tetramethylammoniumhydroxide).

Next, the substrate W after the cap plating treatment is transferred tothe cleaning/drying treatment section 88 to carry out a cleaning/dryingtreatment of the substrate, and the cleaned substrate W is returned bythe transfer device 92 to a cassette in the loading/unloading section80.

Though this embodiment shows, as a cap plating treatment, the case ofpreviously activating the exposed surface of copper film 7 by adheringPd thereto, and then carrying out an electroless Co—W—P plating toselectively cover the activated copper surface with a Co—W—P alloy film,the present invention, of course, is not limited to such an embodiment.

Though the above-described embodiments relate to electroless platingapparatuses, the present invention is of course applicable toelectrolytic plating apparatuses in which a plating current is allowedto flow between an anode and a cathode, which are immersed in a platingsolution, to form a plated film.

As described hereinabove, according to the present invention, byproviding the plating bath of a double bath structure consisting of theinner and outer baths and disposing a heating device in the outer bath,the plating apparatus can be simplified and the footprint can be madesmall. Further, since a plating solution in the inner bath can beheat-insulated and kept warm by the plating solution in the outer bath,the plating solution can be controlled at a uniform temperature duringplating and a uniform plated film can be formed with ease on the platingsurface of a workpiece.

FIG. 7 is a plan view of an example of a substrate plating apparatus.The substrate plating apparatus comprises loading/unloading sections510, each pair of cleaning/drying sections 512, first substrate stages514, bevel-etching/chemical cleaning sections 516 and second substratestages 518, a washing section 520 provided with a mechanism forreversing the substrate through 180°, and four plating apparatuses 522.The plating substrate apparatus is also provided with a firsttransferring device 524 for transferring a substrate between theloading/unloading sections 510, the cleaning/drying sections 512 and thefirst substrate stages 514, a second transferring device 526 fortransferring a substrate between the first substrate stages 514, thebevel-etching/chemical cleaning sections 516 and the second substratestages 518, and a third transferring device 528 for transferring thesubstrate between the second substrate stages 518, the washing section520 and the plating apparatuses 522.

The substrate plating apparatus has a partition wall 523 for dividingthe plating apparatus into a plating space 530 and a clean space 540.Air can individually be supplied into and exhausted from each of theplating space 530 and the clean space 540. The partition wall 523 has ashutter (not shown) capable of opening and closing. The pressure of theclean space 540 is lower than the atmospheric pressure and higher thanthe pressure of the plating space 530. This can prevent the air in theclean space 540 from flowing out of the plating apparatus and canprevent the air in the plating space 530 from flowing into the cleanspace 540.

FIG. 8 is a schematic view showing an air current in the platingsubstrate apparatus. In the clean space 540, a fresh external air isintroduced through a pipe 543 and pushed into the clean space 540through a high-performance filter 544 by a fan. Hence, a down-flow cleanair is supplied from a ceiling 545 a to positions around thecleaning/drying sections 512 and the bevel-etching/chemical cleaningsections 516. A large part of the supplied clean air is returned from afloor 545 b through a circulation pipe 552 to the ceiling 545 a, andpushed again into the clean space 540 through the high-performancefilter 544 by the fan, to thus circulate in the clean space 540. A partof the air is discharged from the cleaning/drying sections 512 and thebevel-etching/chemical cleaning sections 516 through a pipe 546 to theexterior, so that the pressure of the clean space 540 is set to be lowerthan the atmospheric pressure.

The plating space 530 having the washing sections 520 and the platingapparatuses 522 therein is not a clean space (but a contamination zone).However, it is not acceptable to attach particles to the surface of thesubstrate. Therefore, in the plating space 530, a fresh external air isintroduced through a pipe 547, and a down-flow clean air is pushed intothe plating space 530 through a high-performance filter 548 by a fan,for thereby preventing particles from being attached to the surface ofthe substrate. However, if the entire flow of the down-flow clean air issupplied by only an external air supply and exhaust, then enormous airsupply and exhaust are required. Therefore, the air is dischargedthrough a pipe 553 to the exterior, and a large part of the down-flow issupplied by circulating air through a circulation pipe 550 extended froma floor 549 b, in such a state that the pressure of the plating space530 is maintained to be lower than the pressure of the clean space 540.

Thus, the air returned to a ceiling 549 a through the circulation pipe550 is pushed again into the plating space 530 through thehigh-performance filter 548 by the fan. Hence, a clean air is suppliedinto the plating space 530 to thus circulate in the plating space 530.In this case, air containing chemical mist or gas emitted from thewashing sections 520, the plating sections 522, the third transferringdevice 528, and a plating solution regulating bath 551 is dischargedthrough the pipe 553 to the exterior. Thus, the pressure of the platingspace 530 is controlled so as to be lower than the pressure of the cleanspace 540.

The pressure in the loading/unloading sections 510 is higher than thepressure in the clean space 540 which is higher than the pressure in theplating space 530. When the shutters (not shown) are opened, therefore,air flows successively through the loading/unloading sections 510, theclean space 540, and the plating space 530, as shown in FIG. 9. Airdischarged from the clean space 540 and the plating space 530 flowsthrough the ducts 552, 553 into a common duct 554 (see FIG. 10) whichextends out of the clean room.

FIG. 10 shows in perspective the substrate plating apparatus shown inFIG. 7, which is placed in the clean room. The loading/unloadingsections 510 includes a side wall which has a cassette transfer port 555defined therein and a control panel 556, and which is exposed to aworking zone 558 that is compartmented in the clean room by a partitionwall 557. The partition wall 557 also compartments a utility zone 559 inthe clean room in which the substrate plating apparatus is installed.Other sidewalls of the substrate plating apparatus are exposed to theutility zone 559 whose air cleanness is lower than the air cleanness inthe working zone 558.

FIG. 11 is a plan view of another example of a substrate platingapparatus. The substrate plating apparatus shown in FIG. 11 comprises aloading unit 601 for loading a semiconductor substrate, a copper platingchamber 602 for plating a semiconductor substrate with copper, a pair ofwater cleaning chambers 603, 604 for cleaning a semiconductor substratewith water, a chemical mechanical polishing unit 605 for chemically andmechanically polishing a semiconductor substrate, a pair of watercleaning chambers 606, 607 for cleaning a semiconductor substrate withwater, a drying chamber 608 for drying a semiconductor substrate, and anunloading unit 609 for unloading a semiconductor substrate with aninterconnection film thereon. The substrate plating apparatus also has asubstrate transfer mechanism (not shown) for transferring semiconductorsubstrates to the chambers 602, 603, 604, the chemical mechanicalpolishing unit 605, the chambers 606, 607, 608, and the unloading unit609. The loading unit 601, the chambers 602, 603, 604, the chemicalmechanical polishing unit 605, the chambers 606, 607, 608, and theunloading unit 609 are combined into a single unitary arrangement as anapparatus.

The substrate plating apparatus operates as follows: The substratetransfer mechanism transfers a semiconductor substrate W on which aninterconnection film has not yet been formed from a substrate cassette601-1 placed in the loading unit 601 to the copper plating chamber 602.In the copper plating chamber 602, a plated copper film is formed on asurface of the semiconductor substrate W having an interconnectionregion composed of an interconnection trench and an interconnection hole(contact hole).

After the plated copper film is formed on the semiconductor substrate Win the copper plating chamber 602, the semiconductor substrate W istransferred to one of the water cleaning chambers 603, 604 by thesubstrate transfer mechanism and cleaned by water in one of the watercleaning chambers 603, 604. The cleaned semiconductor substrate W istransferred to the chemical mechanical polishing unit 605 by thesubstrate transfer mechanism. The chemical mechanical polishing unit 605removes the unwanted plated copper film from the surface of thesemiconductor substrate W, leaving a portion of the plated copper filmin the interconnection trench and the interconnection hole. A barrierlayer made of TiN or the like is formed on the surface of thesemiconductor substrate W, including the inner surfaces of theinterconnection trench and the interconnection hole, before the platedcopper film is deposited.

Then, the semiconductor substrate W with the remaining plated copperfilm is transferred to one of the water cleaning chambers 606, 607 bythe substrate transfer mechanism and cleaned by water in one of thewater cleaning chambers 606, 607. The cleaned semiconductor substrate Wis then dried in the drying chamber 608, after which the driedsemiconductor substrate W with the remaining plated copper film servingas an interconnection film is placed into a substrate cassette 609-1 inthe unloading unit 609.

FIG. 12 shows a plan view of still another example of a substrateplating apparatus. The substrate plating apparatus shown in FIG. 12differs from the substrate plating apparatus shown in FIG. 11 in that itadditionally includes a copper plating chamber 602, a water cleaningchamber 610, a pretreatment chamber 611, a protective layer platingchamber 612 for forming a protective plated layer on a plated copperfilm on a semiconductor substrate, water cleaning chambers 613, 614, anda chemical mechanical polishing unit 615. The loading unit 601, thechambers 602, 602, 603, 604, 614, the chemical mechanical polishingunits 605, 615, the chambers 606, 607, 608, 610, 611, 612, 613, and theunloading unit 609 are combined into a single unitary arrangement as anapparatus.

The substrate plating apparatus shown in FIG. 12 operates as follows: Asemiconductor substrate W is supplied from the substrate cassette 601-1placed in the loading unit 601 successively to one of the copper platingchambers 602, 602. In one of the copper plating chambers 602, 602, aplated copper film is formed on a surface of a semiconductor substrate Whaving an interconnection region composed of an interconnection trenchand an interconnection hole (contact hole). The two copper platingchambers 602, 602 are employed to allow the semiconductor substrate W tobe plated with a copper film for a long period of time. Specifically,the semiconductor substrate W may be plated with a primary copper filmaccording to electroless plating in one of the copper plating chambers602, and then plated with a secondary copper film according toelectroplating in the other copper plating chamber 602. The substrateplating apparatus may have more than two copper plating chambers.

The semiconductor substrate W with the plated copper film formed thereonis cleaned by water in one of the water cleaning chambers 603, 604.Then, the chemical mechanical polishing unit 605 removes the unwantedportion of the plated copper film from the surface of the semiconductorsubstrate W, leaving a portion of the plated copper film in theinterconnection trench and the interconnection hole.

Thereafter, the semiconductor substrate W with the remaining platedcopper film is transferred to the water cleaning chamber 610, in whichthe semiconductor substrate W is cleaned with water. Then, thesemiconductor substrate W is transferred to the pretreatment chamber611, and pretreated therein for the deposition of a protective platedlayer. The pretreated semiconductor substrate W is transferred to theprotective layer-plating chamber 612. In the protective layer platingchamber 612, a protective plated layer is formed on the plated copperfilm in the interconnection region on the semiconductor substrate W. Forexample, the protective plated layer is formed with an alloy of nickel(Ni) and boron (B) by electroless plating.

After the semiconductor substrate is cleaned in one of the watercleaning chambers 613, 614, an upper portion of the protective platedlayer deposited on the plated copper film is polished off to planarizethe protective plated layer, in the chemical mechanical polishing unit615.

After the protective plated layer is polished, the semiconductorsubstrate W is cleaned by water in one of the water cleaning chambers606, 607, dried in the drying chamber 608, and then transferred to thesubstrate cassette 609-1 in the unloading unit 609.

FIG. 13 is a plan view of still another example of a substrate platingapparatus. As shown in FIG. 13, the substrate plating apparatus includesa robot 616 at its center which has a robot arm 616-1, and also has acopper plating chamber 602, a pair of water cleaning chambers 603, 604,a chemical mechanical polishing unit 605, a pretreatment chamber 611, aprotective layer plating chamber 612, a drying chamber 608, and aloading/unloading station 617 which are disposed around the robot 616and positioned within the reach of the robot arm 616-1. A loading unit601 for loading semiconductor substrates and an unloading unit 609 forunloading semiconductor substrates is disposed adjacent to theloading/unloading station 617. The robot 616, the chambers 602, 603,604, the chemical mechanical polishing unit 605, the chambers 608, 611,612, the loading/unloading station 617, the loading unit 601, and theunloading unit 609 are combined into a single unitary arrangement as anapparatus.

The substrate plating apparatus shown in FIG. 13 operates as follows:

A semiconductor substrate to be plated is transferred from the loadingunit 601 to the loading/unloading station 617, from which thesemiconductor substrate is received by the robot arm 616-1 andtransferred thereby to the copper plating chamber 602. In the copperplating chamber 602, a plated copper film is formed on a surface of thesemiconductor substrate which has an interconnection region composed ofan interconnection trench and an interconnection hole. The semiconductorsubstrate with the plated copper film formed thereon is transferred bythe robot arm 616-1 to the chemical mechanical polishing unit 605. Inthe chemical mechanical polishing unit 605, the plated copper film isremoved from the surface of the semiconductor substrate W, leaving aportion of the plated copper film in the interconnection trench and theinterconnection hole.

The semiconductor substrate is then transferred by the robot arm 616-1to the water-cleaning chamber 604, in which the semiconductor substrateis cleaned by water. Thereafter, the semiconductor substrate istransferred by the robot arm 616-1 to the pretreatment chamber 611, inwhich the semiconductor substrate is pretreated therein for thedeposition of a protective plated layer. The pretreated semiconductorsubstrate is transferred by the robot arm 616-1 to the protective layerplating chamber 612. In the protective layer plating chamber 612, aprotective plated layer is formed on the plated copper film in theinterconnection region on the semiconductor substrate W. Thesemiconductor substrate with the protective plated layer formed thereonis transferred by the robot arm 616-1 to the water cleaning chamber 604,in which the semiconductor substrate is cleaned by water. The cleanedsemiconductor substrate is transferred by the robot arm 616-1 to thedrying chamber 608, in which the semiconductor substrate is dried. Thedried semiconductor substrate is transferred by the robot arm 616-1 tothe loading/unloading station 617, from which the plated semiconductorsubstrate is transferred to the unloading unit 609.

FIG. 14 is a view showing the plan constitution of another example of asemiconductor substrate processing apparatus. The semiconductorsubstrate processing apparatus is of a constitution in which there areprovided a loading/unloading section 701, a plated Cu film forming unit702, a first robot 703, a third cleaning machine 704, a reversingmachine 705, a reversing machine 706, a second cleaning machine 707, asecond robot 708, a first cleaning machine 709, a first polishingapparatus 710, and a second polishing apparatus 711. A before-platingand after-plating film thickness measuring instrument 712 for measuringthe film thicknesses before and after plating, and a dry state filmthickness measuring instrument 713 for measuring the film thickness of asemiconductor substrate W in a dry state after polishing are placed nearthe first robot 703.

The first polishing apparatus (polishing unit) 710 has a polishing table710-1, a top ring 710-2, a top ring head 710-3, a film thicknessmeasuring instrument 710-4, and a pusher 710-5. The second polishingapparatus (polishing unit) 711 has a polishing table 711-1, a top ring711-2, a top ring head 711-3, a film thickness measuring instrument711-4, and a pusher 711-5.

A cassette 701-1 accommodating the semiconductor substrates W, in whicha via hole and a trench for interconnect are formed, and having a seedlayer formed thereon, is placed on a loading port of theloading/unloading section 701. The first robot 703 takes out thesemiconductor substrate W from the cassette 701-1, and carries thesemiconductor substrate W into the plated Cu film forming unit 702 wherea plated Cu film is formed. At this time, the film thickness of the seedlayer is measured with the before-plating and after-plating filmthickness measuring instrument 712. The plated Cu film is formed bycarrying out hydrophilic treatment of the face of the semiconductorsubstrate W, and then Cu plating. After formation of the plated Cu film,rinsing or cleaning of the semiconductor substrate W is carried out inthe plated Cu film forming unit 702.

When the semiconductor substrate W is taken out from the plated Cu filmforming unit 702 by the first robot 703, the film thickness of theplated Cu film is measured with the before-plating and after-platingfilm thickness measuring instrument 712. The results of its measurementare recorded in a recording device (not shown) as record data on thesemiconductor substrate, and are used for determination of anabnormality of the plated Cu film forming unit 702. After measurement ofthe film thickness, the first robot 703 transfers the semiconductorsubstrate W to the reversing machine 705, and the reversing machine 705reverses the semiconductor substrate W (the surface on which the platedCu film has been formed faces downward) The first polishing apparatus710 and the second polishing apparatus 711 perform polishing in a serialmode and a parallel mode. Next, polishing in the serial mode will bedescribed.

In the serial mode polishing, a primary polishing is performed by thepolishing apparatus 710, and a secondary polishing is performed by thepolishing apparatus 711. The second robot 708 picks up the semiconductorsubstrate W on the reversing machine 705, and places the semiconductorsubstrate W on the pusher 710-5 of the polishing apparatus 710. The topring 710-2 attracts the semiconductor substrate W on the pusher 710-5 bysuction, and brings the surface of the plated Cu film of thesemiconductor substrate W into contact with a polishing surface of thepolishing table 710-1 under pressure to perform a primary polishing.With the primary polishing, the plated Cu film is basically polished.The polishing surface of the polishing table 710-1 is composed of foamedpolyurethane such as IC1000, or a material having abrasive grains fixedthereto or impregnated therein. Upon relative movements of the polishingsurface and the semiconductor substrate W, the plated Cu film ispolished.

After completion of polishing of the plated Cu film, the semiconductorsubstrate W is returned onto the pusher 710-5 by the top ring 710-2. Thesecond robot 708 picks up the semiconductor substrate W, and introducesit into the first cleaning machine 709. At this time, a chemical liquidmay be ejected toward the face and backside of the semiconductorsubstrate W on the pusher 710-5 to remove particles therefrom or to makeit difficult for particles to adhere thereto.

After completion of cleaning in the first cleaning machine 709, thesecond robot 708 picks up the semiconductor substrate W, and places thesemiconductor substrate W on the pusher 711-5 of the second polishingapparatus 711. The top ring 711-2 attracts the semiconductor substrate Won the pusher 711-5 by suction, and brings the surface of thesemiconductor substrate W, which has the barrier layer formed thereon,into contact with a polishing surface of the polishing table 711-1 underpressure to perform the secondary polishing. The constitution of thepolishing table is the same as the top ring 711-2. With this secondarypolishing, the barrier layer is polished. However, there may be a casein which a Cu film and an oxide film left after the primary polishingare also polished.

A polishing surface of the polishing table 711-1 is composed of foamedpolyurethane such as IC1000, or a material having abrasive grains fixedthereto or impregnated therein. Upon relative movements of the polishingsurface and the semiconductor substrate W, polishing is carried out. Atthis time, silica, alumina, ceria, or the like is used as abrasivegrains or slurry. A chemical liquid is adjusted depending on the type offilm to be polished.

Detection of an end point of the secondary polishing is performed bymeasuring the film thickness of the barrier layer mainly with the use ofthe optical film thickness measuring instrument, so that detecting afilm thickness which has become zero, or a surface of an insulating filmcomprising SiO₂, shows up. Furthermore, a film thickness measuringinstrument with an image processing function is used as the filmthickness measuring instrument 711-4 provided near the polishing table711-1. By use of this measuring instrument, measurement of the oxidefilm is made, the results are stored as processing records of thesemiconductor substrate W, and are used for judging whether thesemiconductor substrate W in which secondary polishing has been finishedcan be transferred to a subsequent step or not. If the end point of thesecondary polishing is not reached, re-polishing is performed. Ifover-polishing has been performed beyond a prescribed value due to anyabnormality, then the semiconductor substrate processing apparatus isstopped to avoid the next polishing so that defective products will notincrease.

After completion of the secondary polishing, the semiconductor substrateW is moved to the pusher 711-5 by the top ring 711-2. The second robot708 picks up the semiconductor substrate W on the pusher 711-5. At thistime, a chemical liquid may be ejected toward the face and backside ofthe semiconductor substrate W on the pusher 711-5 to remove particlestherefrom or make it difficult for particles to adhere thereto.

The second robot 708 carries the semiconductor substrate W into thesecond cleaning machine 707 where cleaning of the semiconductorsubstrate W is performed. The constitution of the second cleaningmachine 707 is also the same as the constitution of the first cleaningmachine 709. The face of the semiconductor substrate W is scrubbed withthe PVA sponge rolls using a cleaning liquid comprising pure water towhich a surface active agent, a chelating agent, or a pH regulatingagent is added. A strong chemical liquid such as DHF is ejected from anozzle toward the backside of the semiconductor substrate W to performetching of the diffused Cu thereon. If there is no problem of diffusion,scrubbing cleaning is performed with the PVA sponge rolls using the samechemical liquid as that used for the face.

After completion of the above cleaning, the second robot 708 picks upthe semiconductor substrate W and transfers it to the reversing machine706, and the reversing machine 706 reverses the semiconductor substrateW. The semiconductor substrate W which has been reversed is picked up bythe first robot 703, and transferred to the third cleaning machine 704.In the third cleaning machine 704, megasonic water excited by ultrasonicvibrations is ejected toward the face of the semiconductor substrate Wto clean the semiconductor substrate W. At this time, the face of thesemiconductor substrate W may be cleaned with a known pencil type spongeusing a cleaning liquid comprising pure water to which a surface activeagent, a chelating agent, or a pH regulating agent is added. Thereafter,the semiconductor substrate W is dried by spin-drying.

As described above, if the film thickness has been measured with thefilm thickness measuring instrument 711-4 provided near the polishingtable 711-1, then the semiconductor substrate W is not subjected tofurther processing and is accommodated into the cassette placed on theunloading port of the loading/unloading section 701.

FIG. 15 is a view showing the plan constitution of another example of asemiconductor substrate processing apparatus. The substrate processingapparatus differs from the substrate processing apparatus shown in FIG.14 in that a cap plating unit 750 is provided instead of the plated Cufilm forming unit 702 in FIG. 14.

A cassette 701-1 accommodating the semiconductor substrates W formedwith a plated Cu film is placed on a load port of a loading/unloadingsection 701. The semiconductor substrate W taken out from the cassette701-1 is transferred to the first polishing apparatus 710 or secondpolishing apparatus 711 in which the surface of the plated Cu film ispolished. After completion of polishing of the plated Cu film, thesemiconductor substrate W is cleaned in the first cleaning machine 709.

After completion of cleaning in the first cleaning machine 709, thesemiconductor substrate W is transferred to the cap plating unit 750where cap plating is applied onto the surface of the plated Cu film withthe aim of preventing oxidation of the plated Cu film due to theatmosphere. The semiconductor substrate to which cap plating has beenapplied is carried by the second robot 708 from the cap plating unit 750to the second cleaning machine 707 where it is cleaned with pure wateror deionized water. The semiconductor substrate after completion ofcleaning is returned into the cassette 701-1 placed on theloading/unloading section 701.

FIG. 16 is a view showing the plan constitution of still another exampleof a semiconductor substrate processing apparatus. The substrateprocessing apparatus differs from the substrate processing apparatusshown in FIG. 15 in that an annealing unit 751 is provided instead ofthe first cleaning machine 709 in FIG. 15.

The semiconductor substrate W, which is polished in the polishing unit710 or 711, and cleaned in the second cleaning machine 707 describedabove, is transferred to the cap plating unit 750 where cap plating isapplied onto the surface of the plated Cu film. The semiconductorsubstrate to which cap plating has been applied is carried by the secondrobot 708 from the cap plating unit 750 to the second cleaning machine707 where it is cleaned.

After completion of cleaning in the second cleaning machine 707, thesemiconductor substrate W is transferred to the annealing unit 751 inwhich the substrate is annealed, whereby the plated Cu film is alloyedso as to increase the electromigration resistance of the plated Cu film.The semiconductor substrate W to which annealing treatment has beenapplied is carried from the annealing unit 751 to the second cleaningmachine 707 where it is cleaned with pure water or deionized water. Thesemiconductor substrate W after completion of cleaning is returned intothe cassette 701-1 placed on the loading/unloading section 701.

FIG. 17 is a view showing a plan layout constitution of another exampleof the substrate processing apparatus. In FIG. 17, portions denoted bythe same reference numerals as those in FIG. 14 show the same orcorresponding portions. In the substrate processing apparatus, a pusherindexer 725 is disposed close to a first polishing apparatus 710 and asecond polishing apparatus 711. Substrate placing tables 721, 722 aredisposed close to a third cleaning machine 704 and a plated Cu filmforming unit 702, respectively. A robot 723 is disposed close to a firstcleaning machine 709 and the third cleaning machine 704. Further, arobot 724 is disposed close to a second cleaning machine 707 and theplated Cu film forming unit 702, and a dry state film thicknessmeasuring instrument 713 is disposed close to a loading/unloadingsection 701 and a first robot 703.

In the substrate processing apparatus of the above constitution, thefirst robot 703 takes out a semiconductor substrate W from a cassette701-1 placed on the load port of the loading/unloading section 701.After the film thicknesses of a barrier layer and a seed layer aremeasured with the dry state film thickness measuring instrument 713, thefirst robot 703 places the semiconductor substrate W on the substrateplacing table 721. In the case where the dry state film thicknessmeasuring instrument 713 is provided on the hand of the first robot 703,the film thicknesses are measured thereon, and the substrate is placedon the substrate placing table 721. The second robot 723 transfers thesemiconductor substrate W on the substrate placing table 721 to theplated Cu film forming unit 702 in which a plated Cu film is formed.After formation of the plated Cu film, the film thickness of the platedCu film is measured with a before-plating and after-plating filmthickness measuring instrument 712. Then, the second robot 723 transfersthe semiconductor substrate W to the pusher indexer 725 and loads itthereon.

[Serial Mode]

In the serial mode, a top ring 710-2 holds the semiconductor substrate Won the pusher indexer 725 by suction, transfers it to a polishing table710-1, and presses the semiconductor substrate W against a polishingsurface on the polishing table 710-1 to perform polishing. Detection ofthe end point of polishing is performed by the same method as describedabove. The semiconductor substrate W after completion of polishing istransferred to the pusher indexer 725 by the top ring 710-2, and loadedthereon. The second robot 723 takes out the semiconductor substrate W,and carries it into the first cleaning machine 709 for cleaning. Then,the semiconductor substrate W is transferred to the pusher indexer 725,and loaded thereon.

A top ring 711-2 holds the semiconductor substrate W on the pusherindexer 725 by suction, transfers it to a polishing table 711-1, andpresses the semiconductor substrate W against a polishing surface on thepolishing table 711-1 to perform polishing. Detection of the end pointof polishing is performed by the same method as described above. Thesemiconductor substrate W after completion of polishing is transferredto the pusher indexer 725 by the top ring 711-2, and loaded thereon. Thethird robot 724 picks up the semiconductor substrate W, and its filmthickness is measured with a film thickness measuring instrument 726.Then, the semiconductor substrate W is carried into the second cleaningmachine 707 for cleaning. Thereafter, the semiconductor substrate W iscarried into the third cleaning machine 704, where it is cleaned andthen dried by spin-drying. Then, the semiconductor substrate W is pickedup by the third robot 724, and placed on the substrate placing table722.

[Parallel Mode]

In the parallel mode, the top ring 710-2 or 711-2 holds thesemiconductor substrate W on the pusher indexer 725 by suction,transfers it to the polishing table 710-1 or 711-1, and presses thesemiconductor substrate W against the polishing surface on the polishingtable 710-1 or 711-1 to perform polishing. After measurement of the filmthickness, the third robot 724 picks up the semiconductor substrate W,and places it on the substrate placing table 722.

The first robot 703 transfers the semiconductor substrate W on thesubstrate placing table 722 to the dry state film thickness measuringinstrument 713. After the film thickness is measured, the semiconductorsubstrate W is returned to the cassette 701-1 of the loading/unloadingsection 701.

FIG. 18 is a view showing another plan layout constitution of thesubstrate processing apparatus. The substrate processing apparatus issuch a substrate processing apparatus which forms a seed layer and aplated Cu film on a semiconductor substrate W having no seed layerformed thereon, and polishes these films to form interconnects.

In the substrate polishing apparatus, a pusher indexer 725 is disposedclose to a first polishing apparatus 710 and a second polishingapparatus 711, substrate placing tables 721, 722 are disposed close to asecond cleaning machine 707 and a seed layer forming unit 727,respectively, and a robot 723 is disposed close to the seed layerforming unit 727 and a plated Cu film forming unit 702. Further, a robot724 is disposed close to a first cleaning machine 709 and the secondcleaning machine 707, and a dry state film thickness measuringinstrument 713 is disposed close to a loading/unloading section 701 anda first robot 703.

The first robot 703 takes out a semiconductor substrate W having abarrier layer thereon from a cassette 701-1 placed on the load port ofthe loading/unloading section 701, and places it on the substrateplacing table 721. Then, the second robot 723 transfers thesemiconductor substrate W to the seed layer forming unit 727 where aseed layer is formed. The seed layer is formed by electroless plating.The second robot 723 enables the semiconductor substrate having the seedlayer formed thereon to have the thickness of the seed layer measured bythe before-plating and after-plating film thickness measuring instrument712. After measurement of the film thickness, the semiconductorsubstrate is carried into the plated Cu film forming unit 702 where aplated Cu film is formed.

After formation of the plated Cu film, its film thickness is measured,and the semiconductor substrate is transferred to a pusher indexer 725.A top ring 710-2 or 711-2 holds the semiconductor substrate W on thepusher indexer 725 by suction, and transfers it to a polishing table710-1 or 711-1 to perform polishing. After polishing, the top ring 710-2or 711-2 transfers the semiconductor substrate W to a film thicknessmeasuring instrument 710-4 or 711-4 to measure the film thickness. Then,the top ring 710-2 or 711-2 transfers the semiconductor substrate W tothe pusher indexer 725, and places it thereon.

Then, the third robot 724 picks up the semiconductor substrate W fromthe pusher indexer 725, and carries it into the first cleaning machine709. The third robot 724 picks up the cleaned semiconductor substrate Wfrom the first cleaning machine 709, carries it into the second cleaningmachine 707, and places the cleaned and dried semiconductor substrate onthe substrate placing table 722. Then, the first robot 703 picks up thesemiconductor substrate W, and transfers it to the dry state filmthickness measuring instrument 713 in which the film thickness ismeasured, and the first robot 703 carries it into the cassette 701-1placed on the unload port of the loading/unloading section 701.

In the substrate processing apparatus shown in FIG. 18, interconnectsare formed by forming a barrier layer, a seed layer and a plated Cu filmon a semiconductor substrate W having a via hole or a trench of acircuit pattern formed therein, and polishing them.

The cassette 701-1 accommodating the semiconductor substrates W beforeformation of the barrier layer is placed on the load port of theloading/unloading section 701. The first robot 703 takes out thesemiconductor substrate W from the cassette 701-1 placed on the loadport of the loading/unloading section 701, and places it on thesubstrate placing table 721. Then, the second robot 723 transfers thesemiconductor substrate W to the seed layer forming unit 727 where abarrier layer and a seed layer are formed. The barrier layer and theseed layer are formed by electroless plating. The second robot 723brings the semiconductor substrate W having the barrier layer and theseed layer formed thereon to the before-plating and after-plating filmthickness measuring instrument 712 which measures the film thicknessesof the barrier layer and the seed layer. After measurement of the filmthicknesses, the semiconductor substrate W is carried into the plated Cufilm forming unit 702 where a plated Cu film is formed.

FIG. 19 is a view showing a plan layout constitution of another exampleof the substrate processing apparatus. In the substrate processingapparatus, there are provided a barrier layer forming unit 811, a seedlayer forming unit 812, a plated film forming unit 813, an annealingunit 814, a first cleaning unit 815, a bevel and backside cleaning unit816, a cap plating unit 817, a second cleaning unit 818, a first alignerand film thickness measuring instrument 841, a second aligner and filmthickness measuring instrument 842, a first substrate reversing machine843, a second substrate reversing machine 844, a substrate temporaryplacing table 845, a third film thickness measuring instrument 846, aloading/unloading section 820, a first polishing apparatus 821, a secondpolishing apparatus 822, a first robot 831, a second robot 832, a thirdrobot 833, and a fourth robot 834. The film thickness measuringinstruments 841, 842, and 846 are units, have the same size as thefrontage dimension of other units (plating, cleaning, annealing units,and the like), and are thus interchangeable.

In this example, an electroless Co—B plating apparatus can be used asthe barrier layer forming unit 811, an electroless Cu plating apparatusas the seed layer forming unit 812, and an electroplating apparatus asthe plated film forming unit 813.

FIG. 20 is a flow chart showing the flow of the respective steps in thepresent substrate processing apparatus. The respective steps in theapparatus will be described according to this flow chart. First, asemiconductor substrate taken out by the first robot 831 from a cassette820 a placed on the load and unload section 820 is placed in the firstaligner and film thickness measuring instrument 841, in such a statethat its surface, to be plated, faces upward. In order to set areference point for a position at which film thickness measurement ismade, notch alignment for film thickness measurement is performed, andthen film thickness data on the semiconductor substrate before formationof a Cu film are obtained.

Then, the semiconductor substrate is transferred to the barrier layerforming unit 811 by the first robot 831. The barrier layer forming unit811 is such an apparatus for forming a barrier layer on thesemiconductor substrate by electroless Ru plating, and the barrier layerforming unit 811 forms an Ru film as a film for preventing Cu fromdiffusing into an interlayer insulator film (e.g. SiO₂) of asemiconductor device. The semiconductor substrate discharged after thecleaning and drying steps is transferred by the first robot 831 to thefirst aligner and film thickness measuring instrument 841, where thefilm thickness of the semiconductor substrate (i.e., the film thicknessof the barrier layer) is measured.

The semiconductor substrate after film thickness measurement is carriedinto the seed layer forming unit 812 by the second robot 832, and a seedlayer is formed on the barrier layer by electroless Cu plating. Thesemiconductor substrate discharged after the cleaning and drying stepsis transferred by the second robot 832 to the second aligner and filmthickness measuring instrument 842 for determination of a notchposition, before the semiconductor substrate is transferred to theplated film forming unit 813, which is an impregnation plating unit, andthen notch alignment for Cu plating is performed by the film thicknessmeasuring instrument 842. If necessary, the film thickness of thesemiconductor substrate before formation of a Cu film may be measuredagain in the film thickness measuring instrument 842.

The semiconductor substrate which has completed notch alignment istransferred by the third robot 833 to the plated film forming unit 813where Cu plating is applied to the semiconductor substrate. Thesemiconductor substrate discharged after the cleaning and drying stepsis transferred by the third robot 833 to the bevel and backside cleaningunit 816 where an unnecessary Cu film (seed layer) at a peripheralportion of the semiconductor substrate is removed. In the bevel andbackside cleaning unit 816, the bevel is etched in a preset time, and Cuadhering to the backside of the semiconductor substrate is cleaned witha chemical liquid such as hydrofluoric acid. At this time, beforetransferring the semiconductor substrate to the bevel and backsidecleaning unit 816, film thickness measurement of the semiconductorsubstrate may be made by the second aligner and film thickness measuringinstrument 842 to obtain the thickness value of the Cu film formed byplating, and based on the obtained results, the bevel etching time maybe changed arbitrarily to carry out etching. The region etched by beveletching is a region which corresponds to a peripheral edge portion ofthe substrate and has no circuit formed therein, or a region which isnot utilized finally as a chip although a circuit is formed. A bevelportion is included in this region.

The semiconductor substrate discharged after the cleaning and dryingsteps in the bevel and backside cleaning unit 816 is transferred by thethird robot 833 to the substrate reversing machine 843. After thesemiconductor substrate is turned over by the substrate reversingmachine 843 to cause the plated surface to be directed downward, thesemiconductor substrate is introduced into the annealing unit 814 by thefourth robot 834 for thereby stabilizing an interconnection portion.Before and/or after annealing treatment, the semiconductor substrate iscarried into the second aligner and film thickness measuring instrument842 where the film thickness of a copper film formed on thesemiconductor substrate is measured. Then, the semiconductor substrateis carried by the fourth robot 834 into the first polishing apparatus821 in which the Cu film and the seed layer of the semiconductorsubstrate are polished.

At this time, desired abrasive grains or the like are used, but fixedabrasive may be used in order to prevent dishing and enhance flatness ofthe face. After completion of primary polishing, the semiconductorsubstrate is transferred by the fourth robot 834 to the first cleaningunit 815 where it is cleaned. This cleaning is scrub-cleaning in whichrolls having substantially the same length as the diameter of thesemiconductor substrate are placed on the face and the backside of thesemiconductor substrate, and the semiconductor substrate and the rollsare rotated, while pure water or deionized water flows over thesubstrate, thereby performing cleaning of the semiconductor substrate.

After completion of the primary cleaning, the semiconductor substrate istransferred by the fourth robot 834 to the second polishing apparatus822 where the barrier layer on the semiconductor substrate is polished.At this time, desired abrasive grains or the like are used, but fixedabrasive may be used in order to prevent dishing and enhance flatness ofthe face. After completion of the secondary polishing, the semiconductorsubstrate is transferred by the fourth robot 834 again to the firstcleaning unit 815 where scrub-cleaning is performed. After completion ofcleaning, the semiconductor substrate is transferred by the fourth robot834 to the second substrate reversing machine 844 where thesemiconductor substrate is reversed to cause the plated surface to bedirected upward, and then the semiconductor substrate is placed on thesubstrate temporary placing table 845 by the third robot.

The semiconductor substrate is transferred by the second robot 832 fromthe substrate temporary placing table 845 to the cap plating unit 817where cap plating is applied onto the Cu surface with the aim ofpreventing oxidation of Cu due to the atmosphere. The semiconductorsubstrate to which cap plating has been applied is carried by the secondrobot 832 from the cap plating unit 817 to the third film thicknessmeasuring instrument 846 where the thickness of the copper film ismeasured. Thereafter, the semiconductor substrate is carried by thefirst robot 831 into the second cleaning unit 818 where it is cleanedwith pure water or deionized water. The semiconductor substrate aftercompletion of cleaning is returned into the cassette 820 a placed on theloading/unloading section 820.

The aligner and film thickness measuring instrument 841 and the alignerand film thickness measuring instrument 842 perform positioning of thenotch portion of the substrate and measurement of the film thickness.

The seed layer forming unit 812 may be omitted. In this case, a platedfilm may be formed on a barrier layer directly in a plated film formingunit 813.

The bevel and backside cleaning unit 816 can perform an edge (bevel) Cuetching and a backside cleaning at the same time, and can suppressgrowth of a natural oxide film of copper at the circuit formationportion on the surface of the substrate. FIG. 21 shows a schematic viewof the bevel and backside cleaning unit 816. As shown in FIG. 21, thebevel and backside cleaning unit 816 has a substrate holding portion 922positioned inside a bottomed cylindrical waterproof cover 920 andadapted to rotate a substrate W at a high speed, in such a state thatthe face of the substrate W faces upwardly, while holding the substrateW horizontally by spin chucks 921 at a plurality of locations along acircumferential direction of a peripheral edge portion of the substrate,a center nozzle 924 placed above a nearly central portion of the face ofthe substrate W held by the substrate holding portion 922, and an edgenozzle 926 placed above the peripheral edge portion of the substrate W.The center nozzle 924 and the edge nozzle 926 are directed downward. Aback nozzle 928 is positioned below a nearly central portion of thebackside of the substrate W, and directed upward. The edge nozzle 926 isadapted to be movable in a diametrical direction and a height directionof the substrate W.

The width of movement L of the edge nozzle 926 is set such that the edgenozzle 926 can be arbitrarily positioned in a direction toward thecenter from the outer peripheral end surface of the substrate, and a setvalue for L is inputted according to the size, usage, or the like of thesubstrate W. Normally, an edge cut width C is set in the range of 2 mmto 5 mm. In the case where a rotational speed of the substrate is acertain value or higher at which the amount of liquid migration from thebackside to the face is not problematic, the copper film within the edgecut width C can be removed.

Next, the method of cleaning with this cleaning apparatus will bedescribed. First, the semiconductor substrate W is horizontally rotatedintegrally with the substrate holding portion 922, with the substratebeing held horizontally by the spin chucks 921 of the substrate holdingportion 922. In this state, an acid solution is supplied from the centernozzle 924 to the central portion of the face of the substrate W. Theacid solution may be a non-oxidizing acid, and hydrofluoric acid,hydrochloric acid, sulfuric acid, citric acid, oxalic acid, or the likeis used. On the other hand, an oxidizing agent solution is suppliedcontinuously or intermittently from the edge nozzle 926 to theperipheral edge portion of the substrate W. As the oxidizing agentsolution, one of an aqueous solution of ozone, an aqueous solution ofhydrogen peroxide, an aqueous solution of nitric acid, and an aqueoussolution of sodium hypochlorite is used, or a combination of these isused.

In this manner, the copper film, or the like formed on the upper surfaceand end surface in the region of the peripheral edge portion of thesemiconductor substrate W is rapidly oxidized with the oxidizing agentsolution, and is simultaneously etched with the acid solution suppliedfrom the center nozzle 924 and spread on the entire face of thesubstrate, whereby it is dissolved and removed. By mixing the acidsolution and the oxidizing agent solution at the peripheral edge portionof the substrate, a steep etching profile can be obtained, in comparisonwith a mixture of the solutions which is produced in advance beingsupplied. At this time, the copper etching rate is determined by theirconcentrations. If a natural oxide film of copper is formed in thecircuit-formed portion on the face of the substrate, this natural oxideis immediately removed by the acid solution spreading on the entire faceof the substrate according to rotation of the substrate, and does notgrow any more. After the supply of the acid solution from the centernozzle 924 is stopped, the supply of the oxidizing agent solution fromthe edge nozzle 926 is stopped. As a result, silicon exposed on thesurface is oxidized, and deposition of copper can be suppressed.

On the other hand, an oxidizing agent solution and a silicon oxide filmetching agent are supplied simultaneously or alternately from the backnozzle 928 to the central portion of the backside of the substrate.Therefore, copper or the like adhering in a metal form to the backsideof the semiconductor substrate W can be oxidized with the oxidizingagent solution, together with silicon of the substrate, and can beetched and removed with the silicon oxide film etching agent. Thisoxidizing agent solution is preferably the same as the oxidizing agentsolution supplied to the face, because the types of chemicals aredecreased in number. Hydrofluoric acid can be used as the silicon oxidefilm etching agent, and if hydrofluoric acid is used as the acidsolution on the face of the substrate, the types of chemicals can bedecreased in number. Thus, if the supply of the oxidizing agent isstopped first, a hydrophobic surface is obtained. If the etching agentsolution is stopped first, a water-saturated surface (a hydrophilicsurface) is obtained, and thus the backside surface can be adjusted to acondition which will satisfy the requirements of a subsequent process.

In this manner, the acid solution (i.e., etching solution) is suppliedto the substrate to remove metal ions remaining on the surface of thesubstrate W. Then, pure water is supplied to replace the etchingsolution with pure water and remove the etching solution, and then thesubstrate is dried by spin-drying. In this way, removal of the copperfilm in the edge cut width C at the peripheral edge portion on the faceof the semiconductor substrate, and removal of copper contaminants onthe backside are performed simultaneously to thus allow this treatmentto be completed, for example, within 80 seconds. The etching cut widthof the edge can be set arbitrarily (from 2 to 5 mm), but the timerequired for etching does not depend on the cut width.

Annealing treatment performed before the CMP process and after platinghas a favorable effect on the subsequent CMP treatment and on theelectrical characteristics of interconnection. Observation of thesurface of broad interconnection (unit of several micrometers) after theCMP treatment without annealing showed many defects such as microvoids,which resulted in an increase in the electrical resistance of the entireinterconnection. Execution of annealing ameliorated the increase in theelectrical resistance. In the presence of annealing, thininterconnections showed no voids. Thus, the degree of grain growth ispresumed to be involved in these phenomena. That is, the followingmechanism can be speculated: Grain growth is difficult in thininterconnections. In broad interconnections, on the other hand, graingrowth proceeds in accordance with annealing treatment. During theprocess of grain growth, ultra-fine pores in the plated film, which aretoo small to be seen by the SEM (scanning electron microscope), gatherand move upward, thus forming microvoid-like depressions in the upperpart of the interconnections. The annealing conditions in the annealingunit 814 are such that hydrogen (2% or less) is added in a gasatmosphere, the temperature is in the range of 300° C. to 400° C., andthe time is in the range of 1 to 5 minutes. Under these conditions, theabove effects were obtained.

FIGS. 22 and 23 show the annealing unit 814. The annealing unit 814comprises a chamber 1002 having a gate 1000 for taking in and taking outthe semiconductor substrate W, a hot plate 1004 disposed at an upperposition in the chamber 1002 for heating the semiconductor substrate Wto e.g. 400° C., and a cool plate 1006 disposed at a lower position inthe chamber 1002 for cooling the semiconductor substrate W by, forexample, flowing a cooling water inside the plate. The annealing unit814 also has a plurality of vertically movable elevating pins 1008penetrating the cool plate 1006 and extending upward and downwardtherethrough for placing and holding the semiconductor substrate W onthem. The annealing unit further includes a gas introduction pipe 1010for introducing an antioxidant gas between the semiconductor substrate Wand the hot plate 1004 during annealing, and a gas discharge pipe 1012for discharging the gas which has been introduced from the gasintroduction pipe 1010 and flowed between the semiconductor substrate Wand the hot plate 1004. The pipes 1010 and 1012 are disposed on theopposite sides of the hot plate 1004.

The gas introduction pipe 1010 is connected to a mixed gas introductionline 1022 which in turn is connected to a mixer 1020 where a N₂ gasintroduced through a N₂ gas introduction line 1016 containing a filter1014 a, and a H₂ gas introduced through a H₂ gas introduction line 1018containing a filter 1014 b, are mixed to form a mixed gas which flowsthrough the line 1022 into the gas introduction pipe 1010.

In operation, the semiconductor substrate W, which has been carried inthe chamber 1002 through the gate 1000, is held on the elevating pins1008, and the elevating pins 1008 are raised up to a position at whichthe distance between the semiconductor substrate W held on the liftingpins 1008 and the hot plate 1004 becomes e.g. 0.1-1.0 mm. In this state,the semiconductor substrate W is then heated to for example 400° C.through the hot plate 1004 and, at the same time, the antioxidant gas isintroduced from the gas introduction pipe 1010 and the gas is allowed toflow between the semiconductor substrate W and the hot plate 1004 whilethe gas is discharged from the gas discharge pipe 1012, therebyannealing the semiconductor substrate W while preventing its oxidation.The annealing treatment may be completed in about several tens ofseconds to 60 seconds. The heating temperature of the substrate may beselected in the range of 100-600° C.

After the completion of the annealing, the elevating pins 1008 arelowered down to a position at which the distance between thesemiconductor substrate W held on the elevating pins 1008 and the coolplate 1006 becomes for example 0-0.5 mm. In this state, by introducing acooling water into the cool plate 1006, the semiconductor substrate W iscooled by the cool plate to a temperature of 100° C. or lower in e.g.10-60 seconds. The cooled semiconductor substrate is sent to the nextstep.

A mixed gas of N₂ gas with several % of H₂ gas is used as the aboveantioxidant gas. However, N₂ gas may be used singly.

The annealing unit may be placed in the electroplating apparatus.

The cap plating described above is preferably performed by anelectroless plating process, but may be performed by an electroplatingprocess.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

INDUSTRIAL APPLICABILITY

This invention relates to an electroless plating apparatus and methoduseful for forming embedded interconnects in which an electricconductor, such as copper or silver, is imbedded in fine recesses forinterconnects formed in the surface of a substrate like a semiconductorsubstrate, and for forming a protective layer for protecting the surfaceof the interconnects.

1. A plating method, comprising: plating a workpiece in a platingapparatus by allowing a surface to be plated of the workpiece to be incontact with a plating solution, the plating apparatus including; (i) aplating bath having a double bath structure including an inner bath forholding the plating solution and for carrying out said plating, and anouter bath which surrounds the inner bath and is in fluid communicationtherewith; (ii) a heating device disposed in the outer bath so as toheat the plating solution; (iii) a blending system for circulating orstirring the plating solution in the plating bath, the blending systembeing operable to stop functioning during plating of the workpiece; and(iv) a holder for holding a workpiece so that a surface of the workpieceto be plated faces downward, and for rotating the workpiece; stoppingthe functioning of the blending system during said plating; and rotatingthe workpiece during said plating using the holder in a manner tocounteract a natural convection of the heated plating solution so as tobring the plating solution into a stationary state during said plating.2. The plating method according to claim 1, wherein the workpiece isrotated at a speed in a range of 1 rpm to 20 rpm during said plating. 3.The plating method according to claim 2, wherein the blending systemcomprises a plating solution circulation system.
 4. The plating methodaccording to claim 3, wherein the plating solution circulation system isadapted to withdraw the plating solution from the inner bath and returnit to the outer bath.
 5. The plating method according to claim 2,wherein the blending system comprises a stirring device having astirring blade.
 6. The plating method according to claim 5, wherein thestirring device is disposed in almost the center of the inner bath. 7.The plating method according to claim 1, wherein the holder and theblending system are separate and adapted to function independently. 8.The plating method according to claim 1, wherein the heating devicecomprises a heating tube for passing a heating medium therethrough, theheating tube being arranged around a periphery of the inner bath.
 9. Theplating method according to claim 8, further comprising heating theplating solution prior to said plating using the heating tube.